Alternative history is a mainstay of speculative fiction. Redrawing countries' borders is very often a part of that. Sometimes countries that exist in the real world are missing. Sometimes new countries are added. Heck, even real history can make changes that dramatic in less than a decade.
You're asking a two-part question. First, if it's okay to invent a country and stick it in land currently part of another country (in your case, China, and perhaps parts of Russia and Mongolia). Second, if it's okay to give your invented country a personality and history and political actions.
The answer to both questions is yes. It's done all the time. Whether your story is a vision of the future as starting from our present or an alternative history set in the present day or past, or in the future with a different history today, it fits right into speculative fiction's boundaries.
It's possible some of your specifics might upset people to the point of taking legal action. And I'm not familiar with Russian law. While I doubt there's anything that would make your book illegal, I honestly have no idea if that's a risk. In the United States, everything you mention is perfectly legal and rather mundane. That may not be true elsewhere.
I was going to give you a short list of some books you might consider reading with similar aspects, starting with Ecotopia. But it turns out there are hundreds. So many that there's actually a Wikipedia page. Many of the examples on that page are stories about hidden countries (like Oz) or completely fictional places that don't interact with the rest of the world. But some are indeed about countries carved out of existing ones.